As semiconductor devices become progressively smaller, conventional methods of solving existing problems are becoming obsolete. One such problem is to avoid what is referred to as "junction breakdown". Junction breakdown is a phenomenon which short circuits the semiconductor devices such as those used in nonvolatile memory. Another such problem is to increase what is referred to as the "field turn on voltage". Field turn on voltage is the voltage at which the field oxide located between the various transistors or devices, typically located in a memory, allows communication between the devices. It is desirable to provide a field turn on voltage high enough to prevent communication between the various devices.
To increase the junction breakdown voltage, the field implant concentration can be lowered. However, to increase the field turn on voltage, either the field oxide thickness can be increased or the field implant concentration can be increased. If the field implant concentration is increased, however, it will result in an undesirable decrease of the junction breakdown voltage.
The conventional method for increasing the junction breakdown voltage is to lower the field implant concentration. The conventional method for increasing the field turn on voltage is to use a thick field oxide. However, as the semiconductor devices become increasingly smaller, the range of acceptable field oxide thicknesses become increasingly more limited.
For further background information regarding issues involving semiconductor manufacturing, see Silicon Processing for VLSI Era vol. II, Processing Integration, by Stanley Wolf, Lattice Press, 1990; and Semiconductor Devices Physics and Technology, S. M. Sze, 1985, copyright to Bell Labs.
One solution, such as the channel stop implant architecture manufactured by Advanced Micro Devices, Inc., solves the problem of increasing the junction breakdown voltage and increasing the field turn on voltage while limiting the oxide thicknesses. This architecture uses a low field implant concentration to increase junction breakdown voltage and an area with high field implant concentration located away from the source/drain junction to increase the field turn on voltage. Although this architecture is acceptable for many applications, it is dependent upon correct alignment of a mask used in producing the area with the high field implant concentration located away from the source/drain junction. If this mask is misaligned, the high field implant concentration area may be created too close to the source/drain junction, thus decreasing the junction breakdown voltage.
There is a need for a device and method for providing a semiconductor device which provides for a high junction breakdown voltage and a high field turn on voltage which does not require a thick field oxide and is independent of a misalignment of the mask. The present invention addresses such a need.